The present invention relates to an image pickup apparatus, such as a video camera, or an automatic target tracking video camera system including a video camera and, more particularly, to a video camera capable of automatic target tracking and automatic zooming.
Active research and development efforts concerning the automation of the operation of cameras have been made in recent years with the progressive spread of video cameras and camcoder, i.e., video cameras integrally provided with a VCR. Techniques relating to an automatic iris, automatic white balance control and automatic focusing developed through the research and development efforts have been put to practical uses. However, the automation of operations for directing the camera toward a particular object, controlling the direction of the camera to keep the particular object within the angle of view of the camera and zooming to adjust the angle of view has not been practically realized and these operations must be manually carried out.
It has been thought that a detecting means for detecting the position of an object and a camera moving means for directing a camera toward an object are necessary to track a target object and to pick up the image of the target object.
A method relating to the detecting means, disclosed in Japanese Patent Laid-open (Kokai) No. 59-208983 detects a target object on the basis of the movement of the target object determined on the basis of a difference signal representing the positional difference between images taken at a fixed interval. However, when detecting the target object from its movement, the camera will fail to move correctly if an object other than the target object moves because the object other than the target object will be mistakenly detected.
Apparatus, in which an electrically powered pedestal and a camera unit are movable, relating to the camera moving means are proposed in Japanese Patent Laid-open (Kokai) Nos. 59-16357 and 63-72271. These apparatus, however, need a mechanism for moving the camera unit including the pedestal to change the direction of the camera, which inevitably enlarges the scale of the apparatus and increases power consumption. Although these apparatus are capable of tracking a target object in a wide tracking range, these apparatus have a large moment of inertia and are unable to operate at a high response speed. A method disclosed in Japanese Patent Laid-open (Kokai) No. 4-329773 employs an externally drivable optical decentering device, such as a prism having a variable apex angle. A method disclosed in Japanese Patent Laid-open (Kokai) No. 2-210982 controls the mode of driving a solid-state image pickup device electrically. Although this method of controlling the mode of driving the solid-state image pickup device can be practiced by a small-scale apparatus at a high response speed and at a low power consumption, this method is not capable of tracking a target object in a wide tracking range. Thus, each of these previously proposed methods has its merits and demerits and none of them is perfectly satisfactory.
Accordingly, it is an object of the present invention to solve the foregoing problems and to provide an automatic target tracking camera system capable of smoothly and accurately tracking a target object that moves about in a wide range.